In the Patent citation 1, it is described that a laser device guides a laser light emitted by a light projecting portion such as a laser oscillator into a light receiving member such as an optical fiber with aligning manner. In the Patent citation 1, the laser light is aligningly positioned with respect to the optical fiber, by a technique referred to as wobbling which includes oscillating minutely the optical member with a certain amplitude and measuring a variation of the intense of the laser light (a detection output) at the optical fiber to detect an amount of miss-alignment of the laser light and then moving the optical member into a position where the receiving light intense of the laser light will be optimized.
In the case where the optical member is driven by a frictional driving type of driving device using a piezoelectric actuator, the displacement of the optical member can vary with the direction of driving. In this case, a displacement when the optical member is moved the certain small distance forwardly and a displacement when the optical member is moved over the certain small distance backwardly are different from each other. Thereby, an error is caused in an amount of the deviation from a point of the optical member where is calculated from the variation of the laser light intense so as to maximize the laser light intense. Such error can cause problematically a requirement of a number of the wobbling operation repeated to achieve accurate positioning, or a deviation of the optical member that can not be eliminate by the wobbling operation in the case where the driving displacement is large with respect to the variance of the detection output in the wobbling operation.
Also, in the piezoelectric actuator, there is a problem that driving performance will be changed due to an abnormal wear of the driving shaft in its frictionally contacting portion through a repeat of sliding displacements in a small area.
Moreover, the piezoelectric actuator can make driving displacement for each pulse of driving voltage smaller with reducing amplitude of the driving voltage. However, driving voltages smaller than certain amplitude can not cause a sliding displacement, hence it has been a problem that the piezoelectric actuator can not obtain minute displacement.    Patent citation 1: JP 2003-338795 A    Patent citation 2: JP H6-265759 A